Correlation analysis between magnetic susceptibility in MRI and amyloid β in PET

Abstract

AbstractBackgroundStudies on quantitative susceptibility mapping (QSM) have reported increased susceptibility in the brain of Alzheimer’s disease patients, reflecting the pathological accumulation of iron in Aβ plaques. Previously, we revealed moderate correlation between increased magnetic susceptibility in QSM and Aβ deposition in PET by using a region of interest (ROI) analysis in a relatively small cohort (26 patients) (Kudo K., et al. AAIC 2019). In this study, we examine the correlation in a larger sample size by using the ROI analysis and a whole‐brain voxel‐based analysis.MethodForty‐two patients were prospectively recruited in four centers. The clinical diagnoses were as follows: 23 dementia cases, 18 mild cognitive impairment cases, and one cognitively normal case. Magnetic resonance imaging was performed using 3‐T scanners (Hitachi, Ltd.). Amyloid PET imaging was performed using 18F‐flutemetamol. Both QSM and PET images were spatially normalized, and the ROI and voxel‐based analyses were performed to examine correlation between these two images. In the ROI analysis, the correlations were analyzed for 47 regions (defined by an automated anatomical labeling atlas) by using Pearson’s correlation coefficient. In the voxel‐based analysis, the correlation coefficients were calculated between spatially smoothed QSM and PET images on a voxel by voxel basis. This research was supported by AMED under Grant Number JP18he1402002.ResultBased on amyloid PET, 20 patients were Aβ positive and 22 were Aβ negative. In the ROI analysis, positive correlations were noted in 24 of the 47 regions, and moderate correlations (r>0.30) were noted in four regions: the supramarginal gyrus (r=0.35), anterior cingulate gyrus (r=0.32), rectal gyrus (r=0.31), and medial orbitofrontal cortex (r=0.30). When averaged for these four regions, the correlation was moderate (r=0.59), and receiver operator characteristic analysis to predict Aβ positivity revealed that the area under the curve was 0.79. In the voxel‐based analysis, three clusters were found as positively correlated regions (r>0.30) in the parietal and frontal cortices. When averaged for these three clusters, the correlation was high (r=0.80).ConclusionThe ROI‐based and voxel‐based analysis results suggest that the increased susceptibility of QSM was correlated with amyloid PET.